Once a Raj orphan, always a Raj orphan. In Jane Gardam's superb new novel, Sir Edward Feathers, an antediluvian retired judge, enters extreme age carrying his secret wound coiled inside him like a baby. Born in Malaya to a mother who immediately dies and a father whose heart has been petrified by the first world war, Eddie is expelled to the loveless mother-country. He is alone, with the Raj orphan's stiff-upper-lipped anguish as to where "home" is. Shuttlecocked to and fro between institutions and colonies, Eddie's odyssey is a sad mock epic version of the wanderings of the children of the British empire, partly based on the early life of Rudyard Kipling.

Sir Edward is "said to have invented Filth - Failed in London Try Hong Kong", as the Benchers in the Inner Temple muse, having spotted "the old coelocanth" lunching in their midst. A bit of a mystery, they agree, such a magnificent chap, benevolent, popular, and just that one rancorous dispute "with Veneering" that doesn't add up. So who is "Old Filth"? All we have is an empty chair. He has just left. We begin where we end by pondering Filth's absence.

Are you interested in venerable lawyers, the relic of empire? You will be. Do you want to know about the Far Eastern Bar? A reader of Old Filth, despite its unpromising title, will become passionately curious about such matters. This novel is surely Gardam's masterpiece. On the human level, it is one of the most moving fictions I have read for years. I shall always remember the scene in which, putting up at the garish hotel that has replaced The Old Judges' Lodging, this most ramrod-backed and disciplined of elderly men sees his wife's obituary whilst doing his stately breakfasting. He "wept silently behind his hands, sitting in this unknown place", the sole figure in the vastness of the dining room. He weeps on and on. Round him the staff clear the table, change the cloth. "They said not a word."

Rich in such moving perspectives, Old Filth is even richer in its tragicomic style. This is the rare novel that drives its reader for ward while persistently waylaying and detaining by the sheer beauty and inventiveness of its style. One must savour every phrase. The marriage of quirky eccentricity and psychological authenticity is a Gardam technique, but here her cunning wit, moving deftly between scenes and eras, displays the tragedy of a vintage world forever passing away. If Old Filth himself is a death's head in a carnival of vanities, an emotionally crippled remnant of empire, he is not - or not only - the dessicated monster you would expect. Gardam's lively sympathy renders Filth vividly alive in his illustrious isolation.

Veneering's name conjures the hollow arriviste of Dickens's Our Mutual Friend. This figure, Filth's adversary and latterly his close companion, has had a love-affair with Filth's wife, Betty, giving her the sensual tenderness missing from her Raj orphan husband. Nothing in this novel is as odd and moving as the childless and aged Betty's unself-pitying burial of the "guilty pearls", Veneering's gift, while planting tulips for a spring she will never see. "Who shall have you when I am gone?" she asks the pearls. No one. Seizing the moment (she is kneeling and finds it hard to get up), she plants them in a bulb-hole. Much later a new child from next door annoys the widower Filth by landing "at his feet like a football": "What's that in your hand?" Sir Edward asks. "Just some old beads," says the spontaneous lad. "I found them in that flower-bed." Then, Gardam writes, "He vanished." So the seed came up. The barren Betty's pearls (identical to those her husband gave her, and she is sure he never noticed the substitution) are inherited by a child she never had. The beauty of this focused, crisp and understated writing lies in a complex irony that allows the reader insights denied to Edward.

In this drama of last things, the mystery of mortal transience combines with a principle of immortal surprise. An aged man is a babe-in-arms; his childhood is still quick within him and he remains capable of flashes of insight, quirks of impulse. Filth (a name that never ceases to cause the reader a queasy, surprised pang with each recurrence) dies on a final journey "to Malaysia, then up to Borneo. Kotakinakula. Where I was born." As his exequies are tolled by the bell at Temple Bar, Filth's epitaph is given - he is written off - by one of the judges. They are looking at the inscription on a monument in the Inner Temple Garden in London that serves as an epigram for the novel: "Lawyers, I suppose, were children once." The pair of them agree that he was no one very much, deserved no more than a brief epitaph: "Laughable ... Good judge ... Travelling alone. Quite alone."